Download Nano-polymer modified bitumen, Nano Silica Particles, Physical

Journal of Civil Engineering Research 2015, 5(4A): 11-16
DOI: 10.5923/c.jce.201501.03
The Effects of Nano Silica Particles on the
Physical Properties and Storage Stability of
Polymer-Modified Bitumen
Dhawo Ibrahim Alhamali1,*, Nur Izzi Md. Yusoff1, Jiantao Wu2, Quan Liu2, Shaban Ismael Albrka1
1
Dept. of Civil and Structural Engineering, Universiti Kebangsaan Malaysia, Malaysia
2
College of Civil and Transportation Engineering, Hohai Universiti, China
Abstract This study was conducted to investigate the physical and morphological properties and storage stability of
polymer modified bitumen’s (PMB) mixed with nanosilica (NS). Polymer modified bitumen, PG-76 and NS were mixed with
concentration of bitumen’s weight at 0, 2, 4 and 6%. Throughout the process, the binders were regulated at 163°C and
blended using a shear rate of 3000 rpm for 1 hour. Microscopic examinations of the bituminous binders were then carried out
using a scanning electron microscopy (SEM); the SEM images show that the NS particles disperse well in the bituminous
binder matrix. The NS’ effect on the physical properties and an additional NS in the PMB identified to some extent reduced
viscosity and ductility at 2 and 4% of NS, at 6% were stable to increase. Additionally, the NS-PMBs binders softening point
increased and penetration decreased. Furthermore, NS-PMBs binders’ storage stability depended mainly on NS content and
the storage stability succeeded with NS at concentration 6% by weight of bituminous binder. As result, the nanosilica
particles are a good modifier in inhibiting oxidizing reactions in the bitumen binder.
Keywords Nano-polymer modified bitumen, Nano Silica Particles, Physical properties, Storage stability
1. Introduction
Bitumen is made up of complex composition of chemical
that displays viscous and elastic properties equally which
rely comprehensively on time and temperature [1].
Researchers and engineers have tried to utilize different
types of modifiers to amend and better how bitumen
materials perform, together with styrene butadiene styrene
(SBS) [2]. Many researchers have revealed how
polymer-modified bitumens better the possible deficiencies
with the asphalt mixture pavements overall performance [3].
The styrenic block copolymers (e.g. styrene–butadiene–
styrene, SBS) seem to have the highest potential to benefit
bitumen modification [4]. And it was known that the
addition of SBS can improve conventional bitumen
compositions physical and mechanical properties [5].
Nevertheless, the stability of the SBS-modified bitumen
storage is generally poor when temperatures are raised due
to the SBS and bitumen weak compatibility. Several
methods have been established to prepare stable practical
storage SBS-modified bitumen. The succeeding growth
of polymer nanocomposites has caused a great interest in
* Corresponding author:
[email protected] (Dhawo Ibrahim Alhamali)
Published online at http://journal.sapub.org/jce
Copyright © 2015 Scientific & Academic Publishing. All Rights Reserved
academic and industrial communities. Essentially, polymer
nanocomposites are made up of a blend of one or more
polymers with various nanomaterials such as nanoclays,
carbon nanotubes, etc. [6].
The use of nanomaterial in asphalt pavement started
rather late. Nano-technology is utilized as a new material,
device and system at the molecular stage. Several
nano-materials which have been or have the possibility to
be utilized to modify bitumen, such as nano-clay,
nano-silica, nano-hydrated lime, nano-sized plastic powders,
or polymerised powders, nano-fibres, nano-tubes to name a
few [7].
Yao et al. [4] gauge the rheological properties and
bituminous binders which have been modified with nano
are blended with nanosilica chemical bonding. In this
research, adding nanosilica to the control bitumen at
contents 4% and 6% decided on the bituminous binders’
weight. The study showed that the antiaging property,
rutting and fatigue cracking nanosilica modified binders’
performance are improved, and nanosilica added in the
control asphalt mixture considerably betters in terms of
dynamic modulus, flow number, and resistant to rutting
(permanent deformation).
Nano-SiO2 powder and SBS probable benefits were
reported for the asphalt mixtures used on pavements. A
primary study was carried out to determine bituminous
binder and modifiers physical properties. The results of this
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Dhawo Ibrahim Alhamali et al.: The Effects of Nano Silica Particles on the Physical
Properties and Storage Stability of Polymer-Modified Bitumen
investigation showed that the modification of asphalt
mixture by 5% SBS plus 2% nano-SiO2 powder could give
the better results in the tests conducted in the current study,
so this modification can increase bituminous binder and
mixtures physical and mechanical properties [8].
In this paper, laboratory tests of the physical properties
with a number of polymer-modified bitumen (PMB) and
nanosilica (NS) were examined and evaluated. Henceforth,
nanosilica-polymer modified bitumens (NS-PMBs) have
been laboratory produced by mixing with three NS contents.
It was added into PMB at concentrations of 2, 4 and 6% by
weight of PMB. The SEM images produced to show the NS
particles, where, the NS-PMBs tests the conventional
properties, the rotational viscosity (RV) and storage stability
test were carried out for NS-PMBs binders’ characteristics
evaluation.
2. Experimental Design
2.1. Binder
PG-76 (Dorotech Hr-Super) polymer modified bitumen, is
the control sample. The tropical regions climatic conditions
are consistently fair throughout the world and the availability
of performance graded (PG) binder in this region are based
on the higher temperatures. This study does not take into
consideration the environments’ low temperature as the
tropical countries’ temperature seldom drops below 30°C for
the duration of daylight hours and regularly lies within the
range of 35- 45°C.
2.2. Nano-Silica
Silica is a rich international compound that is largely used
in industries producing silica gels, colloidal silica, and fumed
silica, etc. [9]. Nanosilica composites have fascinated several
scientific interests too. The benefit of these nano-materials
existing in low cost production and the high performance
features [10]. According to Yao et al. [4], nanosilica is a
material with a vast surface area, robust adsorption, good
dispersion, high chemical purity and excellent stability.
common modes of operation in SEM analysis are
backscattered electron imaging (BSE), secondary electron
imaging (SEI), and EDS [12]. In this study, BSE was used to
observe the surface morphology and analyses microstructure
characteristics of the PMB and NS-PMBs samples.
2.5. Conventional Physical Properties Tests
Conventional physical tests include penetration test at
25°C [13], softening point [14], ductility at 25°C [15], and
viscosity test using Brookfield viscometer (model DV-II)
[16] were carried out on PMB and NS-PMBs samples.
2.6. Temperature Susceptibility
Changing the temperature susceptibility with NS was
investigated with a calculating penetration index (PI). The
higher the PI value of bitumen, the lower is its temperature
susceptibility. For PI, the temperature susceptibility for the
binders is measured by calculating the PI using the
penetration at 25°C and softening point results. Penetration
index is calculated using Equation 1 [17]:
(1)
where Pen is the penetration test at 25°C and S.P is the
softening point.
2.7. Storage Stability Test
Hot storage stability test is utilized for evaluation of
modified bitumen high temperature storage stability [18].
The binder is empty into an aluminum foil tube 30 cm in
height and 3 cm in diameter. The binder is kept straight up in
an oven at 163 ± 5°C for 48 hours without interruption. Then
the binder is permitted to cool, and it is cut horizontally into
three pieces. The top and the bottom parts are placed
separately into beakers and tested for their softening point. If
the softening point difference is less than 2.5°C, then the
binder can be considered a storage stable [19].
3. Results and Discussion
2.3. Sample Preparation
3.1. Scanning Electron Microscope (SEM)
This nanosilica used to regulate binder was altered in the
laboratory. The addition of nanosilica material into the
control binder at concentrations of (PMB), 2% (NS-PMB2),
4% (NS-PMB4) and 6% (NS-PMB6) by weight of the binder
and mixed in the high shear rate machine. It was detected that
when nanosilica disperses and melts in the control
bituminous binder, the binder’s surface had a few floating
bubbles. While mixed, the binder samples were kept at
163°C and combined using a shear rate of 3000 revolutions
per minute (rpm) for duration of one hour.
The SEM images of nanosilica modified bitumen are
helpful in understanding the microstructure change of
modified bitumen, as well as the physical dispersion of
nanosilica particles. As shown in Figure 1, the SEM images
of NS-PMBs present the well-dispersed nanosilica particles
in the bitumen matrix. Due to the agglomeration of
nanosilica, the surface of nanosilica group reacts with the
PMB. The new structure of nanosilica modified bitumen
binder is formed.
2.4. Scanning Electron Microscope (SEM)
Nanosilica’s effects when it is added on PMB physical
properties as indicated in Table 1. As the penetration values
decrease and the softening points increase with the
SEM, using a focused electron beam to scan the surface of
a sample, generates a variety of signals [11]. The three most
3.2. Conventional Physical Properties
Journal of Civil Engineering Research 2015, 5(4A): 11-16
increasing nanosilica contents, this validates the increased
hardness and stiffness of the NS-PMBs. The higher ductility
value was NS-PMB6, with unstable behavior at value of
NS-PMB2 and NS-PMB4 were lower than PMB. In contrast,
the stability of the behavior when ductility is increased at
13
NS-PMB6 which show the higher ductility value for
NS-PMBs as shown in Table 1. This behavior can be
attributed to be indicative of the different modified chemical
structures of the PMB.
(a)
(b)
(c)
(d)
(e)
Figure 1. SEM images (NS) and (NS-PMBs): (a) SEM image of NS at 400x magnification, (b) SEM image of PMB at 500x magnification, (c) SEM image
of NS-PMB2 at 500x magnification, (d) SEM image of NS-PMB4 at 500x magnification and (e) SEM image of NS-PMB6 at 500x magnification
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Dhawo Ibrahim Alhamali et al.: The Effects of Nano Silica Particles on the Physical
Properties and Storage Stability of Polymer-Modified Bitumen
Figure 2. Rotational viscosities for the PMB and NS-PMBs binders
Figure 3. Softening point differences between bottom and top of the NS-PMBs binders
Journal of Civil Engineering Research 2015, 5(4A): 11-16
Table 1. Conventionally properties of the PMB and NS-PMBs binders
Tests
PMB
NS-PMB2
NS-PMB4
NS-PMB6
66.4
59.4
49.5
38.2
4.11
4.09
3.55
4.02
102
81
93
108
73
75
76
83
Penetration
@ 25°C (d-mm)
Penetration
index (PI)
Ductility
@ 25°C (cm)
Softening
point (°C)
The Rotational viscosities for the PMB and NS-PMBs
binders, shown in Figure 2, clearly shown that when
nanosilica is added in PMB, NS-PMB binders’ viscosity
increases. As result, nanosilica contents increase and
increase the viscosity values.
In the case of NS-PMB4, the effect can be revealing by the
diverse PMB modified chemical structures. Additionally,
NS-PMBs binder mixing process recommends that those
chemical reactions and physical dispersion are prone to
happening, and a new network structure might be formed due
to the nanosilica being temperature resistant. Moreover,
nanosilica has the ability to strengthen PMB binder and
better the recovery’s ability during stress application.
3.3. Temperature Susceptibility
Penetration index (PI) used to approximate the expected
temperature susceptibility for bitumen. The PI value for
base penetration bitumens normally ranges from
approximately -3 (for high temperature susceptible
bitumens) to approximately +7 for highly blown (low
temperature susceptible) bitumens [17]. As indicated in
Table 1, the PI values were obtained nearly comparable
with the addition of NS. Therefore, NS preserve the PMB
temperature susceptibility.
3.4. Storage Stability Test
Hot storage test for the NS-PMBs was carried out to check
its storage stability at high temperatures. Figure 3 shows that
the softening point differed between bottom and top in
NS-PMB6 are less than 2.5°C, showing that these binders
can remain stable if stored at high temperatures. With a
lower percentage of nanosilica (NS-PMB2 and NS-PMB4) a
continuous binder phase with dispersed nanosilica attained.
have chemical reactions and physical dispersion with the
PMB, it was noted at 2 and 4% of nanosilica on NS-PMB2
and NS-PMB4 binders in elastic properties (viscosity and
ductility result). Softening point, ductility and viscosity were
increased and penetration was decreased. Therefore,
nanosilica could improve PMBs performance properties.
Increasing PMB storage stability; this considered as the most
important advantage in high temperature storage stability. It
could obviously be bettered by selecting proper amount of
nanosilica. Moreover, storage stability test results indicated
that 6% of nanosilica content for binder was stable to be used
at high temperatures. To conclude, the nanoslica particles
material is a reputable modifier in inhibiting oxidizing
reactions in the bitumen binder.
ACKNOWLEDGMENTS
The authors express their gratitude to the Universiti
Kebangsaan Malaysia (DLP-2013-028) and the National
Natural Science Foundation of China (No.51108157) for the
financial support of this work.
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